Automatic telephone system



June9, 1925. 1,541,149

E. J ACOBSEN AUTOMATI C TELEPHONE SYSTEM.

June 9, 1925 1,541,149

E. JACOBSEN AUTOMATIC TELEPHONE SYSTEM June 9, 1925. 1,541,149

I E. JACOBSEN AUTOMATIC TELEPHONE SYSTEM Filed March 19, 1917 3 Sheets-Sheet '5 Patented June 9, 1925.

UNITED STATES PATENT OFFICE.

JACOIBSEN, OF EVANSTON, ILLINOIS, ASSIGNOR 'IO AUTOMATIC ELECTRIC COM PANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

AU'I'OIA'IIC TELEPHONE SYSTEM.

Application filed March 19, 1917; Serial No. 155,651

To all whom it may concern:

Be it known that I, EMIL JACOBSEN, a citizen of the United States of America, and a resident of Evanston, county of Cook, and State of Illinois, have invented certain new and useful Improvements in Automatic Telephone Systems, of which the following is a specification.

My invention relates in general to automatic telephone systems, but is concerned more particularly with small systems of this character commonly known as private automatic exchanges. These systems are largely in use by manufacturing or mercantile establishments of various kinds for providing local service between the different departments, and may be, though not necessarily, connected by one or more trunk lines with a main exchange.

In view of the more or less intimate relations of the subscribers, and of a variety of other factors which need not be discussed in detail, the service requirements in these small systems are radically different from those in a public automatic exchange; and it is possible, therefore to omit or depart from certain constructions considered standard in the latter type of exchange with a view to simplifying the apparatus and reducing the first cost. Furthermore certain features wholly undesirable in a. public automatic exchange may add greatly to the efiiciency and usefulness of a private 'exchange and should be incorporated therein if possible without unduly complicating the apparatus. YWith these objects in view I have designed an improved private automatic exchange system involving a number of features believed to be new which will be fully described hereinafter and more specifically pointed out in the appended claims.

he accompanying drawings, and 3, which will be referred to in the s cification which is to follow, should be placed in order, one below the other. with the verilarly provided with one of these Figs. 1, 2,

together with its associated individual connector, being shown in Fig. 1. Fig. 3 shows a trunk line 110111 incoming from and outgoing to the main exchange, and termi'-' nating at the branch in a special switch which may be termed a combination outgoing repeater and incoming connector.

Referring to Fig. 2, the substation A may be of any standard common battery automatic type, except for certain modifications which will be explained, and comprises the usual receiver '2, transmitter 3, switch hook 4, and ringer-5, the latter being preferably of the pulsating current type. The substation is also provided with a calling device of the well ,known tvpe in which a pair of un ulse springs, represented herein by the re erence character CD, is provided, which may be actuated by dial controlled mecha- I nism to produce interruptions of the line circuit in accordance with the digits in a called number. The substation bridge .includes, in addition to the impulse springs and talking instrumentalities above mentioned, a setof shunt springs S, in the calling device, and a ringing push button' PB. The shunt springs S are shifted whenever the dial of the calling device is turned from normal position, and are etl'ective to open the talkin br id e and to ground one side of the line t roug the impulse springs CD. The ush button PB is intended to be actuated y the calling subscriber after he has dialed-the number of a wanted subscriber, and produces the same result.

The line conductors 11 and 12 of the substation A terminate at the private auto- 1 matic exchange switchboard in the indivldual connector switch C, and it may be mentioned that each subscribers line is simindividual connector switches The connector switch C is of the rotary type and resembles in many respects certain well known rotary the calling substation A, and which has been calledsubstation'A; the latter substation,

line or trunk selecting switches, among which may be mentioned the switch shown in the patent to Dietl, No. 1,126,727. Unlike these rotary line switches, however, the connector C does not respond automatically to perform a preliminary trunk selecting operation, but is directively controlled by the calling device at the substation on the line with which it is associated; It comprises, briefiy, a group of five relays, 15 to 19, inclusive, whose functions will be extical lines at the right in alignment; and when so arranged show diagrammatically the essentials of a complete private automatic exchange system embodying the-principles of my invention. More in detail, there is represented in Fig. 2 an individual connector switch C which is associated with operated to establish connection with a plain'ed later, a motor magnet 20, a set of wipers 21 to 24, inclusive, and a bank of contact sets arranged preferably in the arc of a circle. The wipers have the usual double, or triple, construction, depending of course on the number of degrees in the contact bank, in order to permit of their being continuously driven in the same direction while always maintaining connection with some one of the contact sets in the bank. It is. understood that the showing of the wipers and bank in Fig. 2 is purely diagrammatic, the actual construction of these parts being as illustrated in the Dietl patent, above mentioned, or some equivalent arrangement.

In the preferred embodiment of the invention a connector bank consists of thirty one contact sets, four contacts to the set. The two lower contacts in each set are line contacts, the third is the test contact, and the fourth contacts together have the function of restoring the switch to normal position. as will be explained fully in the detailed specification. When in normal position the switch wipers rest in engagement with the first set of contacts, which as shown in the drawing are dead, that is, they have no conductors attached.

The substation A. and other substations,- and their associated individual connector switches, including the connector switch C, are in all respects like the substation A and the connector switch C.

The two way trunk line 110-111 (Fig. 3) extends to the main exchange (not shown) and may terminate the: e in a repeater and line switch as shown in the patent to Martin, No. 1,136,912. At the private automatic exchange this trunk line terminates, as previously mentioned, in the combination repeater and connector E. The switch E comprises a group of relays 100 to 109, inclusive, whose functions will be described in the explanation of the operation; and, like the local connector switches, a motor magnet 120, a set of wi ers 121 to 12 1, inclusive, and a bank of t irt -one contact sets. In fact the mechanica construction of the switch E is substantially like that of the connector C, although because of the difierent duties it has to perform, it is provided with an increased number of relays and with somewhat diti'erent circuits. Any necessa number of trunk lines may be provide although only two are shown in the drawing. These two trunk lines are multipled in the banks of all the local connector switches, being assigned to the second and third contact sets, respectiyely.

The remaining contact sets, beginning with the fourth, and excepting only the tenth and the twentieth, are assigned to local lines. Each subscribers line is multipled in the banks of all the local connector switches and also in the banks of all the incoming connector switches. In this connection it should be metioned that each local line is provided with four normal conduc-.

connector switches, whether local or incoming. The negative line normal 27, however, is only multipled in the banks of the local connectors, while a special negative normal 26 extends to the banks of the incoming connectors. The reason for this arrangement will be explained fully hereinafter.

It has been'mentioned before that the fourth contacts in the connector banks are provided for the purpose of restoring the switches to normal, and it should also be stated at this time that these contacts are not multipled between switches. The fourth contacts of the sets which are assigned-to trunk lines also have the additional function of controlling the selection of an idle trunk line, as will be explained hereinafter, and are wired as follows: Considering the bank of the connector C (Fig. 2), the fourth contacts of all trunk line contact sets except the last are tied together and connectcd to conductor 29. Of course where there are only two trunk lines the conductor 29 would not be multipled. The fourth contact of the last trunk line contact set (in this case the second) is separate from the rest and is connected to conductor 30. The fourth contacts of all the remaining contact sets, exceptthe first, are all multipled together and are connected to conductor 31. The above applies to all the local connectors. 1n the case of the incoming connectors, each connector has all its fourth contacts except the first tied together and connected to a release conductor, which in the case of connector E (Fig. 3) is the conductor .131.

Pulsating current for operating the ringers in the system is supplied from the v1- brating relay 34 by way ofa common ringing lead 33. This relay 34 may be in continuous operation as shown, or if desired, its circuit may be closed over a common starting conductor multipled in the different connectors. The relay 34 is provided with a weighted pendulum like armature by which its rate of vibration may be regulated to about twenty cycles per second. A. busy signaling machine is provided which comprises a low speed interrupter relay 37, operating onthe same principle as relay 34, a-high speed. interrupter relay 35, and an induction coil' 36. The secondary of the induction coil is 0t" low resistance and is connected to thecommon busy lead 32. For supplying operatin and talking current a plurality of batteries are for convenience shown in the dr wings, but it is to be understoodthat there is preferably but one battery having its positive pole connected to ground.

In the description of the operation of the system which will now be proceeded with, it will first be assumed that the subscriber at substation A desires to obtain connection with the subscriber at substation A, whose telephone number, it may be mentioned, is 4. After the operations incident to the establishment and release of the above connection have been described, it will be explained how the subscriber at substation A obtains. connection with a main exchange subscriber over the trunk line shown in Fig. 3; and subsequently, how such main exchange subscriber may obtain connection with a branch subscriber, as for example, the subscriber at substationA', over the same trunk line. Finally an explanation will be made of what I term the conference calling featureof the invention, by virtue of which three or more subscribers may all be connected together at the same time.

'On the removal of the receiver at substation A, a circuit is completed for the line relays 15 and 17 of the connector C over the following path: ground at G, upper winding of relay 17, resting contact of armature .and the said armature, .line conductor 12, receiver 2, transmitter 3, normally closed shunt springs S, push button PB, impulse springs of the calling device CD, swltch hook 4, line conductor 11, contact spring 58 and the contact normally in engagement therewith, and the winding of line relay 15 to battery B. Relays 17 and 15 are both energized upon the closure of the above circuit, the energization of the former relay being of no particular consequence just at present. Relay 15, however, by attracting its lower armature 41, completes a circuit for the slow-acting release relay 16 in an obvious manner, which relay, upon energizing in turn, prepares a circuit for the motor or stepping magnet 20; separates at its armature 44 the conductors 29, 30 and 31: and at its armature 42 con nects ground G to the private normal conductor 28, whereby the line of substation A is made busvin the banks'of all the other connector switches.

Since the desired substation is the substation A the telephone number of which as previously mentioned is 4, the calling subscriber at substation A will now proceed to operate the dial of his callin device in accordance with this digit. en the dial is turned from its normal position, the shunt springs are shifted, whereby the bridge across the line conductors is opened, and ground G is connected with the line conductor 11. These operations due to the shifting of the shunt springs, result in the 'deenergization of the line relay 17 of the connector switch, the relay. 15 remaining energized by ground at G \Vhen the calling device dial is released and returns to normal position a series of four interruptions is produced in the energizing circuit of relay 15, which relayaccordingly deenergizes a corresponding number of times,

transmitting at each deenergization an im-;

net 20 to battery B The stepping magnet 20 responds to these impulses to rotate the wipers 21 to 24, inclusive, until they arrive at the 5th contact set comprising contacts 60 to 63, inclusive, to which. contacts the normal conductors of the called substation A are multipled.

When the dial at the calling substation reaches its normal position, the shunt springs are returned to the position shown in the drawing, whereby the line relay 17 is again energized. The operation now depends upon whether or not the line of substation A is busy. Assuming this line to be idle, as soon as the relay 17 attracts its lower armature 47, an energizing circuit is completed for the wiper switching relay 19 over the following path: ground at G, seconda winding of induction coil 36, armature 4 and its working contact, lower winding of relay 17, lower winding of relay 19, resting contact of armature 51 and the said armature, wiper 22, test contact 61, through the multiple to normal conductor 28, armature 42' and its resting contact, and the resistance 58 to battery B. Relay 19 is energized upon the completion of the above circuit and first closes a locking circuit for itself as follows: grounded conductor '28, armature 52 and its workin contact, and the upper winding of the sai relay to batterv Further results of the energization ofrelay 19 are the opening of its original energizing circuit at the resting contact of armature 51, and the connection of the grounded conductor 28 to wiper 22 by way of the same armature 51 and its working contact, whereby the line of substation A is made busy; the opening of the circuit of the stripping magnet at armatures 54 and 55; an the closure of the line conductors at armatures 53 and 56.

The re uired connection has..now been establishe In order to signal the subscriber at substation A, the calling subscriber will operate his push button PB, thereby permitting relay 17 of his connector switch to deenergize while maintaining vent the release of the switch. Upon the deenergization of relay 17, pulsating current is transmitted to the ringer 5 at substation A over the following path: grounded'battery B', resistance 59, contact springs of pulsator relay 34, working contact of arma-- notified that he is wanted at the telephone.

It is noted that the pulsating ringing current will also cause the relay 17' to vibrate, but this produces no harmful result. Upon the removal of the receiver, the called substation is supplied with talking current from the relays 15 and 17 of the individual connector= switch C, in exactly the same way that the calling substation A is supplied with talking current from the relays 15 and 17 in the individual connector swi ch C. In other words, due to the absence of the" usual cut-of'f relays in the system each subscriber, whether calling or being called, is supplied with talking current from the line relays in his own individual switch.

The complete talking circuit between the two substations has been drawn in heavv lines and will be readily understood without further explanation. It is to be noted that this talking circuit includes the condenser 57 in the connector switch C and the condenser 57 in the connector switch C. I thus employ but one condenser per connector switch, and preferably reverse the connections of the wipers of each switch in order to bring the. condensers associated with the'calling and called substations on opposite sides of the circuit in an established talking connection.

At the termination of the conversation both subscribers will replace their receivers;

When the receiver is hung up at substation A the circuit of the line relays 15 and 17 is broken and these relays are accordingly deenergiz'e'd. relay 15, the circuit of release-relay 16 is broken, and upon the deenergization of this latter, relay ground G is disconnected from the private normal conductor' 28, thereby rendering the line again accessible to incoming calls and also ermitting the relay 19 to deenergize. At t e same time a circuit is completed for thestepping magnet 20, whereby the connector switch C is restored to normal position. This restoring circuit, or release circuit as it may be termed, may be traced over'the following path: ground at Upon the deenergization of 'G, resting contact of armature 39 and the said armatllrqurmature 41 and its resting conta'pt, armature 4'3 and its resting con-' tact, wiper 21, successive multi ly connected fourth contacts engaged there y, conductor 31, armature Hand its right-hand resting tact, the wipers of the connector are rotated step-by-step over all the remaining contact sets in the bank until they finally arrive at the first set of contacts, which is the normal position. This first set of contacts being dead, the circuit of the rotary magnet is interrupted and further operation thereof is prevented. v

It will now be assumed that the substation A was busy when called, and the operations under these circumstances whereby connection to the busy line is prevented and the calling subscriber is given the busy signal will be described. \Vhenever'the line of substation A is busy the test contact 61 (andits multiples) will have aground potential upon it. It follows therefore, that when the line relay 17 energizes as the calling sub-' scribers dial returns to normal, the relay 19 will not be energized by the enga ement of armature 47 of the said relay 1? with its working contact, but instead will be short-circuited and rendered inoperative as long-as the line of substation A continues to beobusy; Connection with the called line is thus prevented. At the same time, the calling subscriber is given the busy signal in the following manner: By the operation of the busy signaling machine an interrupted tone is produced in the following circuit: ground "G secondarv winding of induction coil 36,

armature 47 and its working contact, lower winding of relay 17 and the lower winding of relay 19 to ground on the busy test contact 61. Since the upper winding of rela 17 is inductively related to the lower win. in an interrupted tone is induced in the ca ling subscribers line circuit including the receiver 2, whereby he is notified that the calledline is busy and for the time being connection to the called line will be completed. Again there is nothing to prevent the calling subscriber, when he gets the busy signal, from operating his dial again instead of hanging up his receiver. thereby moving 1is connector switch oil the busy line. While these possibilities would render the system very objectionable for ordinary public exchanges, it has been found that they introduce no real difiiculty in the case of a small private branch exchange. In fact, in certain instances they may even be of advantage.

In the description of the construction of the individual connector switch C it was stated that the switch bank comprised preferably thirty-one sets of contacts, although they are not necesarily limited to this numher, and since a calling device of the character used is capable of sending at each operation a maximum of ten impulses, it Will be queried how the connector is advanced to establish connection with those subscribers lines which terminate in bank contact sets further around than the tenth. Obviously more than one operation of the calling device will be required. To permit successive operations of the switch in order for these lines to be reached, the eleventh and twentyfirst contact sets are left dead, and the digit 0 is prefixed to the numbers of those lines which terminate between the twelfth and twentieth contacts, inclusive; while 00 is prefixed to the numbers of those subscribers lines which terminate in the remaining contact sets. Evidently this scheme can be extended to any reasonable extent, every ten sets of contacts which are added to the connector bank providing for nine additional subscribers lines.

Having explained the process of establishing and releasing a connection between two local subscribers lines. I will now explain briefly the manner in which trunking connections. both outgoing and incoming are established. For this purpose it will first be assumed that the subscriber at substation A desires to connect with a subscriber in the main exchange. All the local subscribers may be furnished with the regular main exchange directories and are instructed that when calling a main exchange subscriber the digit 1 must be prefixed to the directory telephone number. The subscriber at substation A, then, will first proceed tooperate his calling device in accordance with the digit 1, in order to obtain connection with a .main exchange trunk line. In response to' the operation of the calling device for this digit the individual connector switch 0 is operated to rotate its wipers 21 to 24. inclusive, one step into engagement with the contacts to 7 3, inclusive, which is the contact set associated with the first trunk line. Assuming'. for the purposes of this explanation that the first trunk line is busy, there will be a ground potential on the test contact 71 with which the wiper 22 is now in engagement. When therefore the rela 17 energizes upon the return of the cal ing device to normal, the wiper switching relay 19 of the. connector C will be short-circuited as described in the case of calling a busy local line. and will not energize. The connector C does not remain standing on this busy trunk line, however, but is automatically rotated to find an idle trunk line by the closure of a new circuit for the stepping magnet 20 which may be traced as follows: ground on test contact 71, wiper 22 to armature 51, thence by way of the working contact of armature 45 and the said armature, wiper 21, bank contact 70, conductor 29, interrupter contact of magnet 20, armature 55 and its resting contact, and the winding of magnet 20 to battery B The above circuit will be effective to operate the stepping magnet 20 intermittently until the test wiper 22 arrives at a non-busy or ungrounded test contact. Assuming that the second trunk line is idle, when the test wiper22 arrives at test contact 75, the circuit of'the stepping magnet will be broken and the relay 19 will no .'grounded conductor 28 to wiper 22; opens the circuit of the'stepping magnet 20: and closes the line circuit through to the wipers 23 and 24; all as has been previously de scribed. A further result, occurring only when connection is established with a trunk line. is the operation of the relay 18, which is energized upon the attraction of armatures 51 and 55 of relay 19 over the following path: ground at G, working contact of armature 42 and the said armature, working contact of armature 51 and the said armature, working contact of armature 45 and the said armature, wiper 21, bank contact 74, conductor 30, resistance 82, interruptercontact of the magnet '20, winding of relay 18. and the winding of magnet 20 to battery B. Owing to the high resistance of relay 18, the magnet 20 is not energized over the above circuit. Relay 18, upon energizing, establishes a locking circuit for itself as follows: ground at G, working con tact of armature 42 and the said armature, armature 48 and its working contact, windin of relay 18, and the winding of magnet 20 to battery B. As a further result of' its energization, relay 18 disconnects by the attraction of its armatures 49 and 50, the line conductors 11 and 12 from the line relays 15 and 17, respectively, and extends them by a direct metallic connection to the wipers 24 and 23. An energizing circuit is thereupon established for the line relay 102 of the repeater connector E over the following path: ground at G", winding of impedance coil 100, normal conductor 125, bank contact 76, wiper 23, working contact of armature 56 and the said armature, line conductor 12, to and through substation A, line conductor 11, spring 58, armature 49', armature 53 and its working contact, wiper 24, bank contact 77, normal conductor 126, and the winding of the line relay102 to battery B Upon energizing, the line relay '102 completes a circuit for the slow-acting release relay 103 in an obvious manner, which latter relay, upon energizing, connects ground G by way of armature 136 and its working contact to the private normal conductor 128, thereby completing a holding circuit for the relays 18 and 19 of the connector C as follows: ground G", armature 136 andits working contact, normal conductor 128, bank contact 75,- wiper 22, and the armature 51 and its.

working contact to the armature 52, where the circuit divides, one branch extending by way of the upper winding of relay 19 to battery'B, and the other branch extending by way of the armature 48 and its working contact, the winding of relay 18, and the winding of magnet 20 to battery B. When the relay 18 was energized and the line relays 15 and 17 were disconnected, these relays, of course, both deenergized, the deenergization of the former relay resulting also in the deenergization of the slow-acting release relay 16. This latter operation is without ill effect, however, for the holding circuit de- 7 I scribed above has already been established,

and ground G is replaced by ground G (Fig. 3).

Returning now to the repeater connector E, when the relay 103 was energized a bridge was closed across the trunkvline conductors 110 and 111 as follows: line conductor 110, armature 137 and its working contact, armature 139 and its resting contact, upper winding of relay 105, and the armature 133 and its working contact to line conductor 111.' It has been mentioned before that the trunk line 11 0111 terminates at the main exchange in a repeater and a line switch, as disclosed in the patent to Martin, previously referred to. When the bridge is closed across the trunk line conductors at the branch exchange, this line switch is operated in the usual manner to extend connection to an idle first selector. Relay 105, although energized over the line circuit extending to the main exchange, has no circu t at the same time transmits a series of changing function at this time. The inclusion of its upper winding in the brid e is to prevent short-circuiting of the tal ing conductors- Theralling. subscriber may now operate his calling device in "accordance with the directory number of the wanted subscriber, thereby producing a plurality of series of interruptions in' the circuit of the line relay 102. In response to these interruptions of its circuit, relay 102 is deenergized intermittently in accordance with the digits of the called number, and at its armature 133 produces a plurality of series of interruptions in the trunk circuit extending to t e main exchange, whereby a series of main exchange switches are actuated to extend connection to the called subscribers line. These operations are fully described in the Martin patent and need not be discussed in detail. It should be noted, however, that when the line relay 102 repeats a series of interruptions to the main exchange, it also impulses to the relay 104 over the following path: ground at G, armature 132 and its resting contact, armature 135 and its work ing contact, and the lower winding of the relay 104 to battery 13. Relay 104, being slow-acting, is maintained energized during a series of impulses to short-circuit the upper winding of relay 105 included inthe bridge across the trunk line. This operationreduces the resistance and impedance of the trunk circuit extending to the main exchange and results in a better operation of the automatic switches thereat.

The complete talking circuit extending 'from the substation 'A, through the individual connector C, over the normal conductors 125 and 126, and through the condensers 153 and 154 to the trunk line conductors 111110, has been drawn in heavy lines and may be traced without difiiculty. Talking current is supplied to the substation A through the windings of relays 100 and 102 which are bridged across the talking circuit on the local side of the condensers 153 and 154.

When the conversation isfinished the subscriber at substationA will replace his receiver thereby causing the deenergization of line relay 102, followed by the deenergization of the release relay 103. The retrac-.

tion of the armatures of these two relays results in the permanent opening of the bridge across the trunk line, in response to which the connection in the main exchange is released in the usual and well known manner. As a further result of the deenergization of relay 103, ground Gr is disconnected from the holding circuit extending back to relays 18 and 19 in the connector switch C, and these relays, accordingly, are 'deenergized. Bythe deenergization of the relay 19, a circuit. for the stepping magnet 20 is 1 closed over the path previously described (except that it includes initially the bank contact 74, conductor 30, and the resting contact of armature 44), and the switch wipers are thereuponrotated to normal position.

If all the trunk lines extending to the main exchange had been busy, instead "of the last one being idle as assumed in the explanation just given, the connector switch C would nevertheless have stopped upon the contact set associated with the last trunk line. The reason for this operation will be understood when it is recollected that the energizing circuit for the stepping magnet 20 includes the wiper 21, ban (and its multiples, if there be more than two trunk lines) and the conductor 29. Owing to the fact that the bank contact 74 is not connected with the bank contact 70 but is provided with a separate conductor 30, which is joined to the conductor 29 by means of resistance 82, when the wiper 21 arrives at bank contact 74 the circuit for the rotary magnet will include the said resistance 82 and the current in the circuit will be sufficiently reduced to prevent the further ad- Vance of the switch. It appears then that even though the last trunk line is busy, the connector switch 0 will stop on the contact set associated therewith; and since the test contact, as bank contact 7 5, has ground potential upon it, the relay 19 of the connector will be short-circuited and inoperative, and the calling subscriber will be given a busy signal.

I will now describe briefly the operations which take place when a subscriber at the main exchange calls a subscriber at the branch exchange, as, for example, the subscriber at substation A. In the patent to Martin, which has been several times referred to, apparatus and circuits are shown through the medium of which a calling subscriber in one exchange may extenda connection to a repeater, which is adapted to transmit operating impulses over a trunk line extending to a second exchange. Assuming that the second exchange is the private branch exchange, the operation of which is under consideration, the calling subscriberat the main exchange may complete a connection to a subscriber in the branch exchange as follows: When the connection is extended to the'rep'eaterat the main exchange, a relay in the repeater is operated to close a bridge across the trunk conductors 110 and 111 thereby completing a circuit for the line relay 106 of the incoming connector E as follows ground at G, lower winding of relay 106, normallv closed contact springs controlled by the al mature 147, resting" contact of armature 134 and the said armature, conductor111l, bridge at the repeater at the main exchange, concontact energization of relay armature 144 connects ground G to the private normal conductor 128, whereby the trunk line in use is made'busy in the banks of the local connectors.

When the calling subscriber at the distant exchange operates his calling device in accordancewith the number of the wanted subscriber at the branch exchange a series of interruptions in his line circuit are produced -which are repeated in the circuit of the line relay 106 of the incoming connector -E. T e relay 106 is therefore deenergized a number of times and at each 'deenergization sends an impulse over the following circuit to the stepping magnet 120': ground at G, armature 143 and its resting contact,'arr nature 145 and its lefthand working contact, armature 151 and its resting contact, and the winding of the stepping magnet 120 to battery B. Responsive to these impulses the steppingmagnet 120 is actuated to rotate the wipers "121 to 124, inclusive, until they arrive at the 5th .set of contacts, comprising contacts 160 to 163, inclusive. At the same time that the line relay 106 sends impulses to the stepping magnet 120, it also sends impulses to the relay 104 over the following circuit: ground at G armature 143 and its resting contact, armature 145 and its right-hand working contact, and the lower winding of the relay 104 to battery B. The relay 104 being slow-acting, it retains its armatures during a series of impulses. and at the ,upper "armature 140 connects its upper winding-with the .test wiper 122. When therefore at the end of the series 'of impulses the test wiper 122 stopsin engagement with the test contact 161, if the line of substation A is busy and will be completed via the test wiper 122 by means of which the relay104 ismaintained energized. This circuit extends as'follows: ground on test contact 161, test wiper 122, spring 155 and the contact normally en gaged thereby, armature 140 and its working contact, and the upper winding of relay 104 to battery B. By the continued 104 the busy lead .32

is connected to the upper conductor 1103s there is aground potential upon the test contact 161, a circuit followszconductor 32, armature 138 and its working contact, condenser 1'56, and the rest-- ingcontact of armature 137 and the said armature, to conductor 110. In this manner the calling subscriber at the distant exchange is given a busy signal to advise him that the line of substation A at the branch exchange is inaccessible.

\Ve have assumed, however, that the line of substation A was idle when called, in which case, upon the cessation of impulses in the lower winding of relay 104, the said relay will deenergize, whereupon a circuit for the relay 109 will be completed as follows: ground at G, working contact of armature 144 and the said armature, lower winding of relay 109, rest-ing contact of armature 140 and the said armature, normally closed contact of spring 155, wiper 122, bank contact 161, normal conductor 28, armature 42 and its resting contact, and the resistance 58 to battery '13. Relay 109 is energized over the above circuit and at its armature 150 closes a locking circuit extending. from ground G through its upper winding, and at the same time armature 150 opens its original energizing circuit and connects ground Gr direct to the test wiper 122, thereby rendering the line of substation A busy. Further results of the energization of relay 109, are the opening of the rotary magnet circuit at armature 151 and the closure of the line conductors at armatures 149 and 152.

Connection to the line wipers 123 and 124 having been established by the operation of relay 109, a signaling circuit for actuating the ringer at substation A may be traced as follows: ringing lead 33, resting contact of armature 141 and the said armature, armature 149 and its working contact, wiper 124, bank contact 163, normal conductor 25, line conductor 12, lower switch hook contact, and the ringer 5 to ground G". The ringer 5 will continue to operate over the above circuit until the receiver is removed, when a circuit will be closed for relay 108 of the incoming connector E as follows: ground at G, upper winding of relay 17 resting contact of armature 50 and the said armature, line conductor 12, through the talking bridge at substation A, and the line conductor 11 to the junction point 14, where the circult divides, one branch extendlng through the winding of line relay 15, and the other branch continuing by way of normal conductor 26, bank contact 162, wlper 123, working contact of armature 152 and the said armature, and the lower winding of the relay 108 to battery B1. Current flow in the above circuit, or rather in the branch last traced, serves to energize the relay 108, whereby a circuit is closed for relay 105 as follows: ground at G", worklng contact of armature 148 and the said armature, and the lower winding of the relay 105 to battery B". Upon energizing, relay 105 breaks the ringing circuit at its upper armature 141, and at its lower armature 142 closes a locking circuit for itself as follows: ground at i, working contact of armature 144 and the said armature,armature 142 and its right-hand working contact, and the lower winding of relay 105 to battery 13". The attraction of armature 142 also results in the connection of ground G to the lower terminal of the upper winding of relay 108; from which it follows that as armature 141 engages its working contact, both windings of relay 108 will be connected in bridge of the called subscribers line in multiple with y the line relays of the connector switch C. The circuit may be traced as follows: ground at G, working contact of armature 144 and the said armature, armature 142 and its lefthand working contact, upper winding of relay 108, working contact of armature 141 and the said armature, armature 149 and its working contact, wiper 124, bank contact 163, and normal conductor 25 to line conductor 12 whence the circuit continues through the substation A and back to the lower windin of relay 108 over a circuit previously trace A result of the energization of relay 108 which should be mentioned is the reversal of the trunk line conductors 110111 as regards their connections to the windings of the line relay 106. By this operation the direction of current flow in the trunk circuit is reversed to operate a polarized relay at the repeater in the main exchange for any desired purpose, such as the collection of a coin. or the operation of a meter.

The talking circuit, which has been drawn in heavy lines, has now been completed, and may be traced without difficulty. It will be observed that the talking current for the transmitter at the called substation A is supplied from two difierent points, viz, from the line relays of the connector C and from the bridge relay 108 at the incoming connector E. Thus a branch exchange subscriber when called from the main exchange, is given an increased supply of talking current to compensate for increased length of the conversational circuit.

\Vhen the conversation is finished and the subscribers hang u their receivers connection is released as ollows: The replacement of the receiver by the calling subscriber results in the disconnection of the main exchange switches and the opening of the bridge across the conductors 110 and 111. The line relay 106 of the incoming'connector E is therefore deenergized, followed by the deenergization of the slow-acting release relay 107, and by the deenergization of the relays 105 and 109. Upon the deenergization of the relays 106 and 107, a circuit for the stepping magnet 120 is closed which may be traced as follows: ground at G, armature 143 and its resting contact, armature 145 and its resting contact, conductor 131, contact 160 and similar multiply connected contacts, wiper 121, interrupter contact of tion given in the foregoing pages, it will be recollected that the subscribers lines in the branch exchange are not provided with cutoil relays for disconnecting the line relays.-

on incoming calls, and that when a line is called, therefore, talking currentto the sub station thereon is supplied from the linerelays of the associated individual connector switch. Evidently then, the branch exchange,

subscribers always retain control of their'in dividual connector switches. The result of this arrangement is to permit an indefinite extension of calls, a first subscriber calling a second, the second subscriber then calling the third, and the third subscriber then calling a fourth, etc'., as many subscribers as desired being thus connected in a common talking circuit. This possibility of connecting a number of subscribeis together automatically is of great advantage in a small system of the character described, for it permits the head of a concern to confer with a number of department heads simultaneously; and also enables a call to be extended by the operation of the calling device at :1- called substation to another substation 1 in order to reach a party who has left the vicinity of his own telephone and gone to some other department.

Having described my invention, what I consider to be new and desire to have protected by Letters Patent will be pointed out in the appended claims. i

lVhat I claim as my invention is:

1. In a telephone system, a plurality of lines each terminating in an automatic switch, said switches having movable and fixed terminals, normal conductors for each line multipled to the fixed terminals oi. the switches associated with the other lines, a condenser in one line conductor of each line, means for operating any one of said switches to connect its associated line with 1 the normal conductors of another line to scriber, and circuit arrangements such that the completed talking circuit will include the two condensers associated with the calling and called lines, one on each side of the circuit. a y I 3. 'In a telephone system, aline terminating in an automatic switch, a pair of line relays for said switch normally bridged acrosssaid line in series with a battery, a motor magnet in sa1d swltch responsive to one of said relays, a test circuit for determining the idle or busy condition of a called line controlled by the other of said relays, and awinding ofsaid other relay included in said testcircuit.

f4. In a telephone system, a'line terminating in an automatic switch, a pair of line relays for said switch bridged across said line in series wlth a battery, a motor magnet in ,said switches responsive to one of said relays, a test circuit for determining the idle or busy condition of a called-line cont-rolled by the other of said relays, and a circuit for signaling a called subscriber controlled by the sa-idtwo relays jointly;

5. In a telephone. systein a, subscribers line terminating in an automatic connector switch, a pair of line relays in said switch, means for'controlling one of said relays-to operate said switch toconnect with a called line, and means for energizing the other of said relays over the line circuit thereafter to close atest circuit for determining the busy or idle condition of the called line.

6. In a. telephone system, a subscribers line terminating in an automatic connector switch, a pair of line relays in said switch adapted to be energized over the line circuit,

line is idle to complete the connection between the two lines,'and means whereby said.

test circuit is closed by said first relay at the end of said series of interruptions.

7. In a telephone system, a calling subscribers line, means including an automatic connector switch controllable over the said calling line for extending connection to a called line, a switching relay for closing talking circuit conductors in said connector,

a test circuit for energizing said relay if the called line is idle, and a relay energized over the calling subscribers line after the called line is found to close said test circuit,

8. In a telephone system, a calling subscribers line, means including an automatic "connector switch controllable over the said calling line for extending connection to a,

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called line, a switching relay for closing talking circuit conductors in said connector, a test circuit for energizing said relay if the called line is idle, and a relay for closing said test circuit energized over the two sides of the calling line in series after the connector switch has operated.

9. In a telephone system, a calling subscribers line, means including an automatic connector switch controllable over the said calling line for extending connection to a called line, a switching relay for closing talking circuit conductors in said connector, a test circuit for energizing said relay if the called line is idle, a relay controlled over the calling subscribers line after the called line is found to close said test circuit, and means at the substation on the calling line for subsequently deenergizing said last relay to close a signaling circuit over a conductor of the connected called line.

10. In a telephone system, a calling subscribers line, means including an automatic connector switch controllable over the said calling line for extending connection to a called line, a switching relay for closing talking circuit conductors in said connector, a test circuit for energizing said relay if the called line is idle, a relay for closing said test circuit energized over the two sides of the calling line in series after the connector switch has operated, and means at the substation on the calling line for subsequently deenergizing said last relay to close a signaling circuit over a conductor of the connected called line.

11. In a telephone system, an automatic switch, trunk lines accessible to said switch, a circuit for driving said switch over busy trunk lines, and a pair of movable test wipers in said switch included in said circuit in series while the switch is moving over busy trunk lines.

12. In a telephone system, an automatic switch, trunk lines accessible to said switch, means for operating said switch to connect with the first one of said trunk lines, a test circuit including a test wiper of said switch for preventing the completion of the connection if the first trunk line is busy, and a branch of said test circuit including another wiper of said switch for advancing it to the next trunk line.

13. In a telephone system, an automatic switch, a motor magnet for operating said switch to engage successive contacts, and

means comprising a wiper and the said contacts successively engaged thereby for operating said magnet to restore said switch to normal.

14. In a telephone system, subscribers lines, an automatic switch individual to each line, a motor magnet in each switch for operating the same to engage successive contacts, and means in each switch comprising a wiper and the said contacts succcssively engaged thereby for operating the associated motormagnet for releasing purposes.

15. In a telephone system, an automatic switch, a plurality of lines accessible to said switch, a motor magnet adapted to be operated to cause said switch to connect with one of said lines, an auxiliary wiper and bank of contacts in said switch, and means for closing a circuit for said motor magnet including said wiper and successive ones of said contacts to restore said switch to normal. 7

16. In a telephone system, a subscribers line, a relay adapted to supply talking current to said line when the same is called, two connectors having access to said line, means whereby when said line is called via one of said connectors the said line is supplied with talking current solely through the said relay, a battery supply relay in the other of said connectors, and means whereby when the said line is called v ia said last connector talking current is supplied thereto through the said two relays in parallel.

17. In a telephone system, a subscribers line, an inductive winding through which talking current is supplied to said line when the same is called, two link circuits for connecting with said line as a called line, means whereby when said line is called via one of said links talking current is supplied thereto solely through said winding, an inductive winding in the other of said links, and means whereby when said line is called via said last link talking current is supplied thereto through the said two windings in parallel.

18. In a telephone system, a first line and a second line, trunk lines, an automatic progressively movable switch associated with the first line and responsive to impulses transmitted thereover to connect the said first and second lines or to select the first one of said trunk lines, means operating independent of subscriber control in case of a trunk call to select'an idle trunk line if the first is busy, a third line, and another automatic progressively movable switch responsive to impulses transmitted over the second line in case of a call to such line to connect the said first line with said third line.

19. In a telephone system, a first line and a second line, trunk lines, an automatic progressively movable switch individual to the first line responsive to impulses'transmitted thereover to connect the said first and second lines or to select the first one of said trunk lines, means ope'ratin independent of subscriber control in case 0 a trunk call to select an idle trunk line if the first is busy, a third line, and another automatic progressively movable switch individual to said second line and controlled thereover in case of a call to said second line to connect the said first line with said third line.

20. In a telephone system, a first line and a second line, trunk lines, an automatic progressively movable switch individual to the first line and responsive to impulses transmitted thereover to connect the said first and second lines or to select the first one of said trunk lines, means operating independent of the subscriber control in case of a trunk call to select an idle trunk line if the first is busy, a third line, another automatic progressively movable switch individual to .said second line and controlled thereover in case of a call to said second'line to connect the said first line with said third line, and means in each of said switches for supplying talking current to its associated line.

21. In a telephone system, a first line and a second line, trunk lines, an automatic'progressively movable switch individual to the first line and responsive to impulses transmitted thereover to connect the said, first and second lines or to select the first one of said trunk lines, means operating independent of subscriber control in case of a trunk call to select an idle trunk line if the first is busy, a third line, another automatic progressively movable switch individual to said second line and cont-rolled therefrom incase of a call to said second line to connect the first line with said third line, and means including-a relay winding in each switch for supplying talking current to the associated individual line.

22. A first line and'a second line, in auto-- matic progressively movable switch individual to the first line responsive to a series of impulses therefrom to progressively move said switch to connect said first and second lines, a third line, another progressively movable switch individual to said second line responsive to a series of impulses therefrom to progressively move said second switch to connect the first line with said third line, and means controlled over each of said lines to thereafter further continue the progressive movement of their associated switch to return the same to normal position.

23. A telephone system including a subscribers line. an automatic adding-type connector switch individual to said subscribers line controlled over the two sides of the subscribers line in series, a single row or level of bank contacts for said automatic switch, other subscribers linesterminating in said bank contacts. subscriber controlled means for said switch for connecting said first subscribers line to any one of said other subscribers lines, subscriber controlled means for ringing the called substation, and automatic means for moving said switch to normal position.

24. A telephone system including a subscribers telephone line, an automatic addingsaid bank contacts,

type connector. switch individual thereto and controlled over the two sides of the subscribers line in series, bank contacts for said switch, subscribers lines terminating in step-by-step means for said switch for connecting said firstsubscribers line to any of said other subscribers lines, subscriber controlled means for ringing the called substation, and automatic means for operating said step-by-step means to move the wipers of said' switch to a normal position.

I 25. A telephone system including a subscribers telephone line, an automatic switch individual thereto, a pair of line relays for said switch connected to said subscribers,

line, a single level of bank contacts for said switch, other subscribers linesconnected to said bank contacts, an impulse sending device for operating one only of said line relays tocause a connection to be established between said first subscribers line and one of said other subscribers lines, and subscriber controlled means for maintaining said line relay energized and for deenergizing the said. other line relay to signal the called subscriber.

26. A telephone system including a subscribers telephone .line, an automatic switch individual thereto, a pair of line relays for said switch connected to said subscribers line, a single level of bank contacts for said switch, other subscribers lines connected to said bank contacts, animpulse sending device for operating one of said line relays to cause a connection to be established'between said first subscribers line and one of said other subscribers lines, subscriber controlled means for maintaining said line relay energized and for deenergizing the said other line relay to signal the called subscriber, and subscriber controlled means for deenerswitch resumes a normal position.

27. A telephone system including a subscribers telephone line, an automatic switch individual thereto, a pair of line relays for said switch connected to said subscribers line, a single level of bank contacts for said switch,-other subscribers lines connected to said bank contacts, an impulse sending device for' operating oneof said line relays to cause a connection to be established between said first subscribers line and one of said other subscribers lines, subscriber controlled means for maintaining said line relay energized and for deenergizing the said .other line relay. to signal the called sub-- scriber. and automatic means for said switch. controllable by the deenergization of both the said line relays for advancing the wipers of said switch to normal position.

28. In an automatic telephone system, an automatic switch for connecting a calling and a called line, a second switch for con- .gizing both of said line relays, whereby said necting the said calling line with a second called line while said first switch is maintained in operated position, a circuit including the two sides of the calling line in series for controlling said first switch, means for setting said first switch on the first called line responsive to impulses transmitted over said circuit, a circuit including the. two sides of said first called line in series for controlling said second switch, and means for setting said second switch on the second called line responsive to impulses transmitted over said second circuit.

29. In an automatic telephone system, an automatic switch controlled over a calling line to connect with a called line, a second switch controlled over the called line to connect the calling line with a second called line. a pair of line wipers in said first switch by means of which the two line conductors of the calling line are connected, respectively, with the two line conductors of said first called line, and a pair of line wipers in said second switch for completing .the connection from the calling line to the two line conductors of the second called line.

30. In an automatic telephone system, a trunk line connecting a main and a branch exchange and terminating in the branch exchange in an automatic connector switch, means whereby a subscriber in the main exchange can control said switch over the two sides of said trunk line in series to complete a connection to a called line in the branch exchange, and another switch controlled over the called line for then extending the connection to a second called line.

31. An automatic telephone system including a pair of telephone lines provided with individual adding-type connectors, respectively, said lines being temporarily switched together, a relay for each con nector. and means for energizing both of i said relays when a connection is efiected.

32. In a telephone exchange system, a' telephone line, a line switch connected to said line, a line relay for said switch, a stepping magnet, a circuit for operating said stepping magnet, a cutoff relay in series with said stepping magnet and energized when an idle trunk is found to extend said line. and a circuit independent of the windin; of said cutofif relay and including the winding of said stepping magnet for returning said line switch to normal.

33. In a telephone exchange system, a telephone line, a line switch connected to said line, a line relay for said switch, electromagnetic means for moving said switch, a circuit for operating said electromagnetic means. other electromagnetic means in series with the first named electromagnetic means and energized when an idle trunk 18 found to extend said line, and a circuit independent of said other electromagnetic means and including the first named electromagnetic means for returning said line switch to normal.

34. In a telephone exchange system, a telephone line, a line switch connected to said line and having a normal position, a line relay for said switch, a stepping magnet, a circuit for operating said steppin magnet to step said switch fromits norma position, a cutoff relay in series with said stepping magnet and energized when an idle trunk is found to extend said line, and a circuit including said stepping magnet for returning said switch to normal.

35. In a tel phone system, a calling line, a called line, means for establishing a connection between said lines, a 'third line, an automatically operated hunting switch, means controlled by the called subscriber for initiating the hunting movement of said hunting switch to extend the established connection in the direction of the third line, and means COIltIOllTd by the called subscriber for completing the extension of the established connection to said third line.

36. In atelephone system, a link circuit having talking conductors and terminating in an automatic switch, means for operating said switch to connect said conductors with the conductors of a called line, a switching relay controlling normally open contacts in said link conductors, a test circuit for testing called lines, a test wiper, a slow acting relay energized during the operation of said switch and for an instant thereafter, and circuit connections whereby when said slowacting relay is energized the test wiper is included in said test circuit through contacts of said slow relay and whereby. when said slow acting relay is deenergized said test wiper is connected to said switching relay.

37. In. a telephone system, an automatic switch, a wiper for said switch having a primary movement and a variable directively controlled secondary movement, a relay, said wiper being connected to one pole of a source of current by way of a path including said relay while the switch is in normal position, a bank contact accessible'to said wiper and connected to the other pole of said source of current, and means for oper ating said switch to close a circuit for said relay over said path by bringing said wiper into engagement with said bank contact.

38. In a telephone system, an automatic switch having a primary movement and a directively controlled secondary movement,

a relay, a wip r of said switch being connected to one pole of a source of current by way of said relay while the switch is in normal position, contacts arranged in groups accessible to said wiper, one of said contacts being connected to the other pole of said source of current, means for operating said switch in its primary movement to associate said wiper with a particular group of contacts, and for then operating said switch in its Secondary movement to close a circuit .for said relay by bringing said w1per into 'tngagcment' with the contact which is connected with said other pole of said source of'current, and means for disconnecting said wiper from the first mentioned pole of 'pole of a source of current, a relay for connecting said line wi ers to the switch, means for bringing said ine wipers into engagement with the called line and said test wiper into engagement with said test contact, and means tor connecting said linewipers with the switch by energizing said relay over a circuit including said test contact and said test wi er in series.

g 40. n a telephone system, a connector switch having normally disconnected linewipers and a test wiper, a called line accessible to said line wipers, a test contact for said called line accessible to said test wiper, said test contactbeingconnected with one pole of a source of current, a relay for connecting said line wi ers to the switch, means for brmgin said me wipers into engagement with t e called line and said test wiper into engagement with said .test contact, means for connecting said line wipers .with the switch b enerzing said relay over a circuit inclu ing and test contact and said test wiper in series, andmeans for placing a "guarding potential on said test contact over a circuit excluding said relay. 7

41. In" a telephone system, a connector switch having normally disconnected line wipers and a test wiper, acalled line accessible to said line wipers, a test contact for said called line accessible to said test wiper, said test contact being connected with one pole of a source of current, a relay for connecting said line wipers to the switch, means for brm in ment with the called line and said test wiper into engagement with said test contact, means for connecting-said line wipers with the switch b energ zing said relayover a circuit inclu ing said test contact andsaid test wiperin series, means for. placing a guarding potential on said test contact over a circuit excluding said relay, and means including a separate winding on said relay for maintaining it energized.

42. In a telephone system, an automatic switch, a set of wipers for said switch havsaid line wipers into engageing movement only in a single plane, sets of contacts accessible to said wipers, trunk lines terminating in certain of said contact sets, subscribers lines terminating in other of said contact sets, a line relay for controlling. said switch to select one of said trunk lines or .a subscribers line, and a cutoff relay operated only when a trunk line is selected for cutting otl' said line relay.

43. In a. telephone system, a two way trunk line connecting a main exchange and a branch exchange, a device comprising a combined connector and repeater in which said trunk line terminates in the branch exchange, means for operating said device from the to main exchange as a connector to "extend the trunk line to a line in the branch 1 exchange, a test circuit for testing the calledbranch exchange line, means for operating said device as a repeater from the branch exchange to repeat impulses over the trunk line to the main exchange, a'slow acting' relay maintained energized while said device is operating either as a connector or as a repeater, contacts on said relay for controllin said test circuit, and other contacts on sai relay for controlling the impulse repeating circuit.

44. In a telephone system, a rotary connector having a test'wiper and an auxiliary test wiper, lins accessible to said connector, a test contact for each line and an auxiliary testcontact foreach line, amotor magnet in said connector, circuit connections for operating said motor magnet by way of said auxiliary test wiper and the contacts of busy called lines, and means in said connector for making an idle called line busy by placing a-p0tential on the associated test contact by way of said test wiper. v

45. In a telephone system, a rotary connector having a test wi er and an auxiliary test wiper, lines accessi is to said connector, a test contact for each line, a motor magnet in said connector, circuit connections for operating said motor magnet by way of said auxiliary test auxiliary test wiper and the auxiliary test contacts of busy called lines, a wiper connect ng relay, c rcuit connections for operating said wiper connecting relay by way 0:

said test wiper and the test contact 0 idle called ine,

said connecting relay when the same is means'in said switch operated if the first a first oneof said first lines,

and means controlled by operated for making the connected called line busy byplacing a potential on the asone of said lines is busy for causing said switch to automatically select another one of said first lines, circuits for controlling the directive movement of said switch and for starting and stopping the idle line selection, and a plurality of circuit changing switching devices, each having but two posi tions, having sole control ofsaid circuits.

47. In a telephone system, an automatic directively controllable switch havin automatic trunk selecting functions, trun lines accessible to said switch, test contacts for said lines and a co-operating test wiper in said switch, a line switching relay in said switch, a magnet controlling the automatic trunk selection, parallel branch circuits extending from said test wiper through said relay and magnet, respectively, to the opposite poles of the central battery, and means for automatically closing said circuits at the end of the directively controlled movement of said switch.

Signed by me at Chicago, Cook County, State of Illinois, this 13th day of March,

EMIL J ACOBSEN 

